Finally had a chance to use the 70-300L in some extended rain yesterday, coincidently where the 100-400L ingested too much water the last time prompting me to look into this in the first place.

Rain was varying in strength, ranging from almost stopped to heavy showers for many hours. As an average I'd say it was light-medium. Had no moisture problems with the lens at all. I noticed any water landing on the barrel got "pushed" out by the zoom action. I think there might have been a side effect here too, as I tended to set the 70-300L to shortest zoom while moving around, whereas with the 100-400L I just let it flop which exposes more of the lens to rain.

I got caught in a heavy downpour yesterday. While showers were on the forecast, they were expected to be much later in the day so I didn't bring any waterproofing with me. So on this occasion my water resistance broke down before the camera! A summer shirt doesn't cut it...

This is what it looked like when I decided to join everyone else in cover under trees. Because the downpour was so sudden and hard, it didn't get a prolonged soaking but the heavy shower was shrugged off without any impact.

Side note: the camera and lens are not bent like it looks in the photo. I don't know if it is just a perspective effect or maybe the HX9V I used to take the shot has some distortion I haven't noticed before.

I spent New Year`s Eve in Salzburg mainly walking through the city always carrying the camera unprotected on my shoulder (with a nonsealed lens mounted...).
It was constantly snowing at +2°C.
Thanks to my Goretex jacket i remained dry, but my camera was quite wet.
At that point i didn´t care about that because i thought that the weather sealing would do it´s job.
I stopped for a hot drink in a cafe before dusk. The warmth of the restaurant led to condensation
inside the camera and soon afterwards i got an "Error 40" in the top display.
According to Canon this indicates a problem with the batteries/power supply.
Quite nervous i went home, opened every port and let it dry for over a day.
The "Error 40" vanished and only the Sensor Cleaning ("Error 6") refused to work the next couple of hours.
Thank god two days into the new year everything was back to normal and i got off with a slap on the wrist.

I think I posted these already in a different thread, but above is the condensation I get in the 100-400L if I use it in the rain a lot. It dries out if I leave the end caps off for a while. That's also why I got the 70-300L in addition...

Similar to Popo, I have a 7D with a 70-200 f/4 IS and has Sealing, and I was lucky to have gotten this lens because I was about to use my 15-85mm and Im glad I didnt.

I got shot at with a super soaker, attacked with a bucket of water, stood too close to the pool to get hit by splash when people dived into the water and it rained. And I kept shooting, but I did tell off the people who threw water at me.

This is an example of just how sharp these L lenses can get. To be honest, I would never had gotten this shot if it wasnt weather sealed because it was about to rain and some kids just shot at me with a super soaker as I took this shot.

Wow this thread really blows my mind!!!! Just so I won't be caught with my pants down: can I say it is safe to assume that I can keep using my 40D (and future 7D) with my EF 17-40/4 L USM (yes it has a filter on it), EF 24-105 L, and EF 70-200 L without having to worry too much about it breaking down on me in or after heavy rain?

I have heard that using a grip on these models changes everything by the way: is that true or is this of no real influence? I could imagine it does have influence, because there can't be any watersealing in between the grip and the battery compartment it fits into (at least that's what I think).

Sooo glad to see this thread, even after months since there was a post! I was outside today. It was snowing all day, and we had blizzard warnings. The temp was right around the freezing point for much of the day, and it was a heavy, wet snow with frequent heavy gusts of wind. I didn't look for animals today as I didn't want to chase any from their warm holes in this kind of weather, but I couldn't resist going out several times today to take pictures. I have a Canon SX Powershot 150 IS, so no additional lenses, but I kept thinking I'd have to come here and ask about weather-proofing my camera for this kind of weather. Several times I had to find a dry spot on my shirt to wipe the lens and screen so I could see, but except for a few water spots on some pictures, I had no problems taking pictures or with condensation despite multiple trips in and out (for at least an hour at a time). Many many thanks to everyone who posted on this subject and to those who added links. I found it very useful today, and I am sure it will come in very handy as winter starts here again.X

Haven't been here for a while, but thought id share my latest experience in the weather sealing department.

So we all know that we should not use non L lenses on our cameras, even if the rain is only a small drizzle. Well, I am not the most careful individual, so I messed up.After a 30min walk in light rain my 50mm f1.4 and 5D MkII was quite soaked. Even though I did my best to shield it. The result was ER01, unable to communicate with the lens.So the camera actually works fine, but given how it is unable to set the aperture it wont play along as it normally would.

I have had this error before on the 7D, which was a result of me yet again being a fool. Regardless of my foolishness I still know a thing or two about electronics, so I jumped into dismantling the camera and fixed the issue. And now I face the same thing again, please enjoy the pictures and comments:

This is the bottom circuit board that communicates with the lens, the small ribbon cable to the right with a black ring around it is the communication bus. The red, green and black cables to the left of it that also goes into the same place is the power delivery. Left to that the red-black-black-red is the power delivery to this circuit board. There are a lot more cables going around supplying currents and communicating, but those aren't within our scope of interest for this specific fault.What I do want you to look out more closely is the corrosion within the black circles that I have drawn. The corrosion is a slight green, because its copper corrosion, not good. And a clear sign of quite a bit of humidity. Water has in this case traveled between the metal plates between the lens and the camera and into the lower chamber where the circuit board is.

There are quite a few fuses on this circuit board that I measured, they all checked out. These fuses are there to prevent short circuits in case a faulty lens is attached, or if the lens communication pins are otherwise short circuited. The water damage in this case has not been severe enough to case the fuses to blow.

However, there seems to have been some prominent currents a foot. Notice the discoloration on the trace and its size. This trace would allow for quite high currents, that I suspect has caused other components on this board to malfunction.

Let's dig a bit deeper, even though the camera fired up nicely and is reasonably healthy it would be good idea to check the DC/DC power supply. So let us follow the bread crumbs:

This is where the cables leads us, to the DC/DC power supply that delivers power from the battery to the camera. This circuit board has massive RF shields over it to prevent noise from the power conversion circuits to influence the very delicate signals from the CMOS sensor. The shields have been removed prior to taking the following picture, but they are slightly visible in the last one.There are several fuses on this circuit board as well, but they also checked out and there is no water damage nor seemingly damaged traces either.

The fault search has been somewhat fruitful, I am not entirely sure if it's only the lower circuit board that has received damage, but that is what I am replacing. Meanwhile, this is how I have stored my camera in its current state, in separate trays to ease rebuild and in box that I will put a lid on to prevent dust from accumulating.

To be continued... and I am back. Found the fault on in the circuit, I actually took a picture of it without even realizing it. Camera works again, will follow up and edit the post tomorrow!

Here is the follow up:

I don't like when I assume things, here I assumed that the black things on the cable was residue of the corrosion. Which is true, but there was also a burn over trace.

Not a very pretty repair, I will try and replace the whole part in the future.The canon electronics is really solid stuff, everthing seems fine even though a short circuit burnt a trace. Not bad, not bad all, color me impressed.